Corinne S. Abraham

Caffeine supplementation and multiple sprint running performance.

PURPOSE The aim of this study was to examine the effects of caffeine supplementation on multiple sprint running performance. METHODS Using a randomized double-blind research design, 21 physically active men ingested a gelatin capsule containing either caffeine (5 mg x kg(-1) body mass) or placebo (maltodextrin) 1 h before completing an indoor multiple sprint running trial (12 x 30 m; repeated at 35-s intervals). Venous blood samples were drawn to evaluate plasma caffeine and primary metabolite concentrations. Sprint times were recorded via twin-beam photocells, and earlobe blood samples were drawn to evaluate pretest and posttest lactate concentrations. Heart rate was monitored continuously throughout the tests, with RPE recorded after every third sprint. RESULTS Relative to placebo, caffeine supplementation resulted in a 0.06-s (1.4%) reduction in fastest sprint time (95% likely range = 0.04-0.09 s), which corresponded with a 1.2% increase in fatigue (95% likely range = 0.3-2.2%). Caffeine supplementation also resulted in a 3.4-bpm increase in mean heart rate (95% likely range = 0.1-6.6 bpm) and elevations in pretest (+0.7 mmol x L(-1); 95% likely range = 0.1-1.3 mmol x L(-1)) and posttest (+1.8 mmol x L(-1); 95% likely range = 0.3-3.2 mmol x L(-1)) blood lactate concentrations. In contrast, there was no significant effect of caffeine supplementation on RPE. CONCLUSION Although the effect of recovery duration on caffeine-induced responses to multiple sprint work requires further investigation, the results of the present study show that caffeine has ergogenic properties with the potential to benefit performance in both single and multiple sprint sports.

Familiarization and reliability of multiple sprint running performance indices.

The aims of this study were to evaluate the time-course of the familiarization process associated with a test of multiple sprint running performance and to determine the reliability of various performance indices once familiarization had been established. Eleven physically active men (mean age: 21 ± 2 years) completed 4 multiple sprint running trials (12 X 30 m; repeated at 35-s intervals) with 7 days between trials. All testing was conducted indoors, and times were recorded by twin-beam photocells. Results revealed no apparent learning effects as evidenced by no significant (p > 0.05) between-trial differences in measures of fastest or mean 30-m sprint time. Within-subject test–retest reliability determined over 4 trials by coefficient of variation (CV) and intraclass correlation coefficient (ICC) showed excellent reliability for measures of fastest and mean sprint times (CV range: 1.34–2.24%; ICC range: 0.79–0.94). Pre- and posttrial blood lactate concentrations showed good reliability when judged in context with typical values (CV range: 12.08–18.21%; ICC range: 0.72–0.78). In contrast, and in line with previous research, fatigue data showed much greater variability (CV: 26.43%; ICC: 0.66). The results of this study suggest that high degrees of test–retest reliability can be obtained in many multiple sprint running indices without the need for prior familiarization.

Biomechanics of ankle instability. Part 2: Postural sway-reaction time relationship.

PURPOSE To test the hypothesis that ankles with functional instability will demonstrate greater single-limb postural sway (PS) than their contralateral stable joint and stable healthy controls and to examine the relationship between single-limb postural sway and muscular reaction time to a simulated ankle sprain mechanism. METHODS Nineteen male volunteers with a history of unilateral ankle sprain and functional ankle instability (FAI) and 19 healthy male controls performed 12 single-limb PS tests, 3 on each leg with and without vision. Participants provided informed consent. Postural sway data are reported on the FAI groups unstable (UA) and stable ankles (SA), and the control groups dominant (DA) and nondominant ankles (NDA). RESULTS With vision, the UA and SA revealed similar postural control; however, the UA showed greater (P < 0.05) anteroposterior PS than the DA (0.46 cm) and the NDA (0.51 cm). Without vision, the UA showed greater (P < 0.05) medial (2.41 cm) and lateral (2.59 cm) PS than the SA and also showed greater (P < 0.05) medial (2.05 and 2.10 cm, respectively) and lateral (2.28 and 2.26 cm, respectively) than the DA and NDA. The relationship between PS and muscle reaction times, derived from the previous article was calculated. Significant correlations (P < 0.05) were found between the unstable ankle peroneus longus (PL) and peroneus brevis (PB) reaction time and lateral (r = 0.63 and r = 0.81, respectively), medial (r = 0.74 and r = 0.76, respectively), and anterior PS (r = 0.56 and r = 0.55, respectively; P < 0.01). CONCLUSIONS Results reveal postural sway deficits in ankles with FAI. They also demonstrate a significant relationship between PL and PB reaction times and postural sway in UA. Individuals who sustain an acute ankle sprain and those with FAI require rehabilitation that improves proprioception, strengthens the evertors and dorsiflexors, and restores peroneal reaction time.

Creatine supplementation and multiple sprint running performance.

The aim of this study was to examine the effects of short-term creatine monohydrate supplementation on multiple sprint running performance. Using a double-blind research design, 42 physically active men completed a series of 3 indoor multiple sprint running trials (15 3 30 m repeated at 35-second intervals). After the first 2 trials (familiarization and baseline), subjects were matched for fatigue score before being randomly assigned to 5 days of either creatine (4·d−1 × 5 g creatine monohydrate 1 1g maltodextrin) or placebo (4·d−1 × 6 g maltodextrin) supplementation. Sprint times were recorded via twin-beam photocells, and earlobe blood samples were drawn to evaluate posttest lactate concentrations. Relative to placebo, creatine supplementation resulted in a 0.7 kg increase in body mass (95% likely range: 0.02 to 1.3 kg) and a 0.4% reduction in body fat (95% likely range: 20.2 to 0.9%). There were no significant (p > 0.05) between-group differences in multiple sprint measures of fastest time, mean time, fatigue, or posttest blood lactate concentration. Despite widespread use as an ergogenic aid in sport, the results of this study suggest that creatine monohydrate supplementation conveys no benefit to multiple sprint running performance.